Telescoping spring assembly for mattresses and the like

ABSTRACT

A spring assembly includes telescopically adjustable inner and outer members biased in an extension direction by a coil spring. A non-stretch fabric sleeve fitted about an inner diameter and an outer diameter of the coil spring is closed at its opposite ends to apply a compression preload to the coil spring. The fabric sleeve prevents transmission of the preload to the inner and outer telescoping members, thereby eliminating stickiness and the popping sound that are drawbacks of the prior art, and the fabric sleeve also provides general noise reduction when the spring assembly changes length.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. provisionalpatent application Ser. No. 61/536,729, filed on Sep. 20, 2011, thedisclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates generally to mattresses and cushioningdevices for home and/or hospital use, and more particularly to atelescoping spring assembly usable as a component of a mattress orcushioning device.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,996,865 to Sabin describes a mattress structure in whicha support assembly comprises a support plate having an array of mountingholes each receiving a respective telescoping spring assembly. In U.S.Pat. No. 6,996,865, various embodiments of the spring assembly areidentified by the reference numerals 20, 120, 220, 320, and 420. Thevarious spring assembly embodiments are telescoping spring assemblies inthe sense that each has an inner member arranged to be axially slidablewithin an outer tubular member, and a mechanical spring is arrangedwithin the inner and outer members to bias the members in an extensiondirection. The Sabin patent teaches that it is desirable to preload thespring to control firmness. In order to achieve preload, Sabin disclosesthe use of a spacer (e.g., spacers 28, 128, and 228) engaging an end ofthe spring and one of the tubular members, wherein the spacer has anaxial length chosen to provide a desired preload. The spring assembliesmounted on the support plate may have different preload characteristicsachieved by using spacers of different lengths to vary the firmness ofthe mattress in different support zones.

Efforts to commercialize the invention in U.S. Pat. No. 6,996,865 havebeen met with certain design challenges. A significant challenge hasbeen the fact that the preload applied to the coil spring is transmittedto the inner and outer tubular members. Under this design, the inner andouter members are forced into a fully extended condition (absentexternal loading) and are prevented from separating by engagement ofopposing shoulder surfaces on the external wall surface of the innermember and on the internal wall surface of the outer member. As aresult, the frictional engagement between the shoulders of the inner andouter members causes the spring assembly to be “sticky” at times, andthe spring assembly does not always react as intended when an externalload is first applied. Moreover, after an external load is removed froma compressed spring assembly, the biasing force of the coil springimmediately pushes the outer member in the extension direction, and theensuing engagement of opposing shoulder surfaces on the inner and outermembers generates a popping sound that is disruptive to a person atrest.

SUMMARY OF THE INVENTION

The present invention solves both of these challenges, and does so byeliminating the need for a spacer of special length in each springassembly.

The present invention is embodied by a spring assembly comprising atubular outer member including a support end and an open receiving endopposite the support end, and a tubular inner member including aninsertion end and a mounting end opposite the insertion end, wherein theinsertion end of the inner member is received through the open receivingend of the outer member such that the outer member is telescopicallymovable relative to the inner member in a compression direction and anextension direction opposite from the compression direction. The springassembly further comprises a coil spring arranged to bias the outermember in the extension direction relative to the inner member. Inaccordance with the present invention, the spring assembly comprises afabric sleeve fitted about an inner diameter and an outer diameter ofthe coil spring, wherein the fabric sleeve is closed at its oppositeends to apply a compression preload to the coil spring. The fabricsleeve prevents transmission of the preload to the tubular members toeliminate the problems of stickiness and noise when the spring assemblychanges length.

BRIEF DESCRIPTION OF THE DRAWING VIEWS

Features and advantages of embodiment(s) of the present disclosure willbecome apparent by reference to the following detailed description anddrawings, in which:

FIG. 1 is a perspective view of a telescoping spring assembly formed inaccordance with an embodiment of the present invention;

FIG. 2 is an exploded view of the telescoping spring assembly shown inFIG. 1;

FIG. 3 is an exploded view of a support cap subassembly of the springassembly shown in FIG. 1;

FIG. 4 is an end view of the support cap subassembly shown in FIG. 3;

FIG. 5 is an exploded view of a mounting subassembly of the springassembly shown in FIG. 1;

FIG. 6 is an end view of the mounting subassembly shown in FIG. 5; and

FIG. 7 is an end view of a coil spring of the telescoping springassembly, wherein the coil spring is enclosed in a fabric sleeve.

DETAILED DESCRIPTION OF THE INVENTION

A telescoping spring assembly formed in accordance with the presentinvention is shown in FIG. 1 and identified generally by referencenumeral 10. Spring assembly 10 comprises a tubular inner memberincluding an insertion end and a mounting end opposite the insertionend. The mounting end is characterized by a fitting 13 for insertioninto a corresponding mounting hole of a plate (not shown), whereby anarray of closely spaced spring assemblies 10 may be formed to providethe core of a mattress as taught by the aforementioned U.S. Pat. No.6,996,865, the entire disclosure of which is incorporated herein byreference. Spring assembly 10 also comprises a tubular outer member 14including a support end 15 and an open receiving end opposite thesupport end. As may be seen in FIG. 1, the insertion end of inner member12 is received by outer member 14 through the open receiving end of theouter member. As may be understood, outer member 14 is telescopicallymovable relative to inner member 12 in a compression direction toshorten the overall length of spring assembly 10, and in an extensiondirection opposite from the compression direction to extend the overalllength of the spring assembly.

Reference is made now to FIG. 2. Spring assembly 10 further comprises acoil spring 16 arranged to bias outer member 14 in the extensiondirection relative to inner member 12. In the embodiment shown, one endof coil spring 16 bears against a bumper insert 18 disposed at theinsertion end of inner member 12, and an opposite end of coil spring 16bears against another bumper insert 20 disposed in outer member 14axially adjacent to support end 15.

FIGS. 3 and 4 show outer member 14 and bumper insert 20 in furtherdetail. As may be seen, outer member 14 includes a plurality axiallyextending ribs 24 spaced at regular angular intervals about an internalwall of the outer member adjacent the open receiving end of the outermember. In the embodiment shown, bumper insert 20 includes a generallyrigid plastic insert on which an elastically deformable bumper piece 26is mounted to face inner member 12, and a bumper spring 28 is disposedon the opposite side of bumper insert 20 to engage support end 15 ofouter member 14. Bumper spring 28 may be chosen to have greaterstiffness than coil spring 16. FIGS. 5 and 6 show inner member 12 andbumper insert 18 in further detail. Inner member 12 includes acircumferential shoulder 30 around an external wall of the inner memberadjacent the insertion end of the inner member. In the embodiment shown,bumper insert 18 includes a generally rigid plastic having a lip 32sized to engage the insertion end of inner member 12 such that bumperinsert 18 remains located at the insertion end of inner member 12. Anelastically deformable bumper piece 34 is mounted on bumper insert 18 toface bumper insert 20. A bumper spring 36 is disposed on the same sideof bumper insert 18 so that it also faces bumper insert 20. Bumperspring 36 may be chosen to have greater stiffness than coil spring 16.The bumper inserts 18 and 20, and the bumper springs 36 and 28, providestiffer cushioning as spring assembly 10 approaches a fully compressedcondition to prevent “bottoming out” under very heavy external loads.

Airflow into and out of spring assembly 10 during telescoping volumechanges is allowed by passages through the mounting end of inner member12 and the support end of outer member 14, however these passages arenot visible in the drawing views. Such airflow is also allowed bypassages 38 through bumper inserts 18 and 20, and by gaps 40 betweenribs 24 in outer member 14.

Axial separation of outer member 14 and inner member 12 may be preventedunless an intentionally large separation force is applied. In theembodiment shown, axial separation is prevented by engagement ofcircumferential shoulder 30 with the ends of ribs 24 closest to supportend 15. However, as will be understood from the description below, whencoil spring 16 is properly preloaded, outer member 14 freely floats onthe coil spring such that the ends of ribs 24 are slightly spaced fromengagement with shoulder 30 to avoid the sticking problem mentioned inthe background section.

In accordance with the present invention, spring assembly 10additionally comprises a fabric sleeve 22 fitted about an inner diameterand an outer diameter of coil spring 16, wherein fabric sleeve 22 isclosed at its opposite ends to apply a compression preload to coilspring 16. The compression preload applied to spring 16 decreases thelength of the spring enough so that the ends of ribs 24 on outer member14 do not engage shoulder 30 on inner member 12. For example, thecompression preload may be chosen to provide a distance of aboutone-eighth of an inch between the ends of ribs 24 and shoulder 30 whenspring assembly 10 is at rest and free of external loading.

Fabric sleeve 22 may be formed about coil spring 16 in a variety ofways. In one way, the sleeve begins as two separate generallyrectangular sheets of non-stretch fabric, one to fit about the outerdiameter of coil spring 16 and the other to fit about the inner diameterof coil spring 16. If coil spring 16 is a variable stiffness coil springwherein the inner and outer diameters vary along the axial length of thespring, then the outer sheet must fit around the largest outer diameterand the inner sheet must fit within the smallest inner diameter. Eachsheet is folded over onto itself and a lengthwise seam is formed alongoverlapping portions of the sheet to provide a generally tubular sleeveportion of appropriate diameter depending upon whether the sleeveportion is internal or external. The external and internal sleeveportions are then arranged around the outer diameter and inner diameterof coil spring 16, respectively a first circumferential seam may then bemade near one end of coil spring 16 to secure the external sleeveportion to the internal sleeve portion. A preload is applied to coilspring 16 by compressing the coil spring to a predetermined axiallength, and then a second circumferential seam is made near the secondend of the compressed coil spring to secure the external sleeve portionto the internal sleeve portion, thereby confining the coil spring in apreloaded condition.

In another way of fitting fabric sleeve 22 to coil spring 16, the fabricsleeve begins as a single generally rectangular sheet of non-stretchfabric in excess of two times the intended length of preloaded coilspring 16. The single sheet is folded over onto itself and a lengthwiseseam is formed along overlapping portions of the sheet to provide anelongated tubular sleeve portion of appropriate diameter to fit aboutthe outer diameter of coil spring 16. The coil spring is inserted intothe elongated tubular sleeve portion and the sleeve is inverted (turnedinside-out) and fed through the interior of the coil spring. As aresult, one end of the spring will be confined against the foldedsleeve, and the other end of the spring will be near an open end wherethe two unconnected ends of the fabric sleeve are aligned with oneanother. A preload is applied to coil spring 16 by compressing the coilspring to a predetermined axial length, and then a circumferential seamis made to attach the aligned ends of the fabric sleeve to one another,thereby closing the open end to confine the coil spring in a preloadedcondition.

Those skilled in the art will understand that seams may be formed bysewing or by ultrasonic welding, and that the amount of excess fabricmaterial needed to form sleeve 22 may depend on the seam technologyused.

At least two fabrics have been found particularly suitable for use informing fabric sleeve 22. The first is Sparmont 900 needle punchedfabric, which is recommended for coil springs with spring rates of twopounds per inch or less. The second is SW400 sonic welded fabric, whichis recommended for coil springs with spring rates from two to fourpounds per inch. Both fabrics are supplied by NuTex Concepts located at2424 Norwood Street, Lenoir, N.C. 28645. Of course, other fabrics may beused.

As will be understood, the use of fabric sleeve 22 in accordance withthe present invention provides important benefits. Fabric sleeve 22maintains the preload on coil spring 16 so that engagement between innermember 12 and outer member 14 is not necessary for this task. In thisway, the problem of “stickiness” is solved, and the popping sound whenthe spring assembly returns to its extended position is eliminated.Moreover, preload can be determined by selecting a coil spring 16 havinga spring rate and free length such that the coil spring provides adesired preload when compressed by fabric sleeve 22 to a predetermined,known length. The spring rate of coil spring 16 may be a variable springrate to provide lesser firmness during initial compression of springassembly 10 under external loading, followed by somewhat greaterfirmness as the spring assembly compresses further. The performance ofeach spring assembly can be individualized without the need for spacersof different lengths as taught by the prior art. Also, the fabric sleevehelps to dampen and absorb acoustic energy to provide quieter springassembly performance apart from elimination of the popping soundmentioned above.

While the invention has been described in connection with exemplaryembodiments, the detailed description is not intended to limit the scopeof the invention to the particular forms set forth. The invention isintended to cover such alternatives, modifications and equivalents ofthe described embodiment as may be included within the spirit and scopeof the invention.

LIST OF REFERENCE SIGNS

10 Spring assembly

12 Inner member

13 Mount fitting on inner member

14 Outer member

15 Support end of outer member

16 Coil spring

18 Bumper insert of inner member

20 Bumper insert of outer member

22 Fabric sleeve

24 Ribs along internal wall of outer member

26 Bumper piece on bumper insert of outer member

28 Bumper spring on bumper insert of outer member

30 Circumferential shoulder of inner member

32 Lip on bumper insert of inner member

34 Bumper piece on bumper insert of inner member

36 Bumper spring on bumper insert of inner member

38 Airflow passages

40 Gaps between ribs

What is claimed is:
 1. A spring assembly, comprising: a tubular outermember including a support end and an open receiving end opposite thesupport end; an inner member including an insertion end and a mountingend opposite the insertion end, wherein the insertion end is received bythe outer member through the open receiving end of the outer member; theouter member being telescopically movable relative to the inner memberin a compression direction and an extension direction opposite from thecompression direction; a coil spring arranged to bias the outer memberin the extension direction relative to the inner member; and a fabricsleeve fitted about an inner diameter and an outer diameter of the coilspring, wherein the fabric sleeve is closed at its opposite ends toapply a compression preload to the coil spring.
 2. The spring assemblyof claim 1, further comprising a first bumper insert including a rigidhousing on which an elastically deformable bumper piece is mounted and abumper spring, wherein the coil spring has a first end bearing againstthe first bumper insert, the elastically deformable bumper piece beingarranged to face toward the inner member and the bumper spring facingaway from the inner member.
 3. The spring assembly of claim 2, furthercomprising a second bumper insert including a rigid lip, an elasticallydeformable bumper piece, and a bumper spring, wherein the coil springhas a second end bearing against the second bumper insert, theelastically deformable bumper piece and the bumper spring of the secondinsert being arranged to face the first bumper insert.
 4. The springassembly of claim 3, wherein the first bumper insert and the secondbumper insert each include airflow passages.
 5. The spring assembly ofclaim 1, wherein the outer member has an exterior wall and an interiorwall, the interior wall including a plurality of axially extending ribs.6. The spring assembly of claim 5, wherein the plurality of axiallyextending ribs are spaced at regular angular intervals about theinterior wall of the outer member, adjacent the open receiving end ofthe outer member.
 7. The spring assembly of claim 6, wherein the innermember includes an external wall and a circumferential shoulder aroundthe external wall; and wherein the compression preload of the coilspring is such that the axially extending ribs are spaced fromengagement with the circumferential shoulder.
 8. The spring assembly ofclaim 7, wherein the compression preload to the coil spring provides adistance of about one-eighth of an inch between ends of the axiallyextending ribs and the circumferential shoulder when the spring assemblyis at rest and free of external loading.
 9. The spring assembly of claim1, wherein the mounting end of the inner member includes a fitting forinsertion into a corresponding mounting hole of a plate.
 10. A method ofmaking a spring assembly, comprising: providing a tubular outer memberincluding a support end and an open receiving end opposite the supportend; providing an inner member including an insertion end and a mountingend opposite the insertion end; arranging a coil spring to bias theouter member in the extension direction relative to the inner member,the coil spring having a fabric sleeve fitted about an inner diameterand an outer diameter of the coil spring, wherein the fabric sleeve isclosed at its opposite ends to apply a compression preload to the coilspring; and arranging the insertion end such that it is received by theouter member through the open receiving end of the outer member, theouter member being telescopically movable relative to the inner memberin a compression direction and an extension direction opposite from thecompression direction.
 11. The method of claim 10, further comprisingarranging a first bumper insert bearing against a first end of the coilspring, the first bumper insert including a rigid insert on which anelastically deformable bumper piece is mounted and a bumper spring, theelastically deformable bumper piece being arranged to face toward theinner member and the bumper spring facing away from the inner member.12. The method of claim 11, further comprising arranging a second bumperinsert bearing against a second end of the coil spring, the secondbumper insert including a rigid lip, an elastically deformable bumperpiece, and a bumper spring, the rigid lip of the second bumper insertbeing sized to engage the inner member, the elastically deformablebumper piece and the bumper spring of the second insert being arrangedto face the first bumper insert.
 13. The method of claim 12, wherein thefirst bumper insert and the second bumper insert are provided with airapertures.
 14. The method of claim 11, wherein the compression preloadto the coil spring provides a distance of about one-eighth of an inchwhen the spring assembly is at rest and free of external loading. 15.The method of claim 11, wherein the outer member has an exterior walland an interior wall, the interior wall including a plurality of axiallyextending ribs.
 16. The method of claim 15, wherein the inner memberincludes a circumferential shoulder around an external wall of the innermember; and wherein the compression preload of the coil spring is suchthat the axially extending ribs are spaced from engagement with thecircumferential shoulder.